This invention relates to an insulating coating for refractory articles to be applied by spraying or gunning. More particularly, the present invention is directed to an insulating coating for refractory articles adapted to be applied by spraying or gunning, wherein the coating imparts sufficient thermal insulation to the refractory article in high temperature environments. In particular, the present invention is directed to a spray insulating coating for refractory articles, wherein the coating is comprised of a lightweight aggregate, an additive to improve green handling strength, organic fiber, a binder, and a foaming agent.
Refractory articles are often used in high temperature environments and must resist chemical attack, withstand molten metal and slag erosion, thermal shock, physical impact, catalytic heat, and similar adverse conditions. In addition, in some refractory articles, such as casting nozzles, it is desirable to have sufficient insulating properties. Insulating coatings for refractory articles are well known. Currently, insulating coating for refractory articles, which can be effectively used in high temperature environments, have been applied by mechanically fixing or adhering ceramic fiber paper to the refractory articles. In this process, ceramic fiber paper is cut to size and bonded onto the refractory articles with any suitable adhesive. Such a process is labor intensive and requires long periods of time to mechanically apply the ceramic fiber paper adding to the cost of manufacturing insulated refractory articles. Further, the handling, cutting, and bonding of the ceramic fiber paper to the refractory article generates ceramic fibers. These fibers have been classified by IARC, the International Agency for Research on Cancer, as a possible human carcinogen. Therefore, it is apparent that improvements are necessary in the production of insulating coatings for refractory articles to eliminate the use of ceramic fiber paper as the process of applying the ceramic fiber paper to the refractory article is costly and may pose health hazards to those involved in the process.
It is desirable to have an insulating coating for refractory articles which is easy to apply, is cost effective, eliminates any potential health hazards associated with the use of refractory ceramic fibers, and which imparts sufficient insulating properties to the refractory article in high temperature environments.